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At least 19 recordsLinked to original sources
PubMed2026

Approaches to observational study designs and analytical options to evaluate the safety of multi-dose vaccines: a systematic review.

INTRODUCTION: Observational studies require careful considerations when evaluating the safety of multidose vaccines. We reviewed design and analytical approaches in observational studies evaluating the safety of multidose vaccines in the post-licensure phase. METHODS: EMBASE, MEDLINE, Web of Science, and Scopus (2018-2022) were searched for hypothesis-testing studies evaluating the safety of multidose vaccines. Key features from frequently used designs were extracted. RESULTS: Among 123 eligible studies, cohort (46%) and self-controlled case series (SCCS)/self-controlled risk interval (SCRI) (40%) followed by case-control (12%) were the most common designs, and 15% of studies used multiple designs. Among cohort studies evaluating multiple doses, vaccination date (36%) and cohort entry with time-updated exposure status (32%) were frequent approaches used to define time zero. Twenty-eight percent of cohort studies did not report time zero; all but one evaluated COVID-19 vaccine effect on post-delivery and fertility-related outcomes. For SCCS/SCRI, 64% of studies accounted for event-dependent exposures, mainly by including pre-exposure periods (53%) and modified SCCS model (48%), while 20% employed multiple correction strategies. Among studies using multiple designs, 68% reached consistent conclusions. CONCLUSIONS: SCCS/SCRI and cohort designs dominate multidose vaccine safety studies. Clear reporting on time zero in pregnancy and fertility-related cohort studies, and on addressing event-dependent exposures in SCCS/SCRI studies is needed, along with guidance on interpreting results from multiple designs.

Humans↗
PubMed1988

Diet and cancer. Any progress in the interim?

It has been 5 years since the National Research Council (NRC) Committee on Diet, Nutrition and Cancer published "Interim Dietary Guidelines" for the nutritional prevention of cancer. The term "interim" implies that these recommendations should be regarded as temporary, pending more definitive findings from additional scientific research. This article reviews findings relevant to the connections between diet and cancer that have emerged from nutritional epidemiology subsequent to the 1982 the NRC report. Some recent research has supported the earlier work which served as a basis for the interim recommendations, some has not, and additional hypotheses have emerged. There continues to be evidence, although it is inconsistent, that dietary fat may be an important factor in colon cancer, and that something related to fruits and vegetables, perhaps carotene, may lower the risk of lung cancer. However, the hypothesized relationships between dietary fat and breast cancer and between dietary fiber and colon cancer have been less consistently supported by new findings. Meanwhile, a new hypothesis has emerged relating alcohol intake to breast cancer risk, although many important questions remain regarding the age at which alcohol use may affect risk, and the dose above which risk is increased. The last 5 years seem to have been characterized by only slow progress in our understanding of the relationship between diet and cancer. It is clear that in 1988 we are still very much in the interim. Critical methodologic assessments of the reasons for the discrepancies in findings among the various studies, and meta analytic approaches may be helpful in increasing our understanding of the set of epidemiologic research conducted to date. More important, however, are the many types of studies now underway, including more rigorously designed observational studies and chemo-preventive and dietary-preventive trials. These studies will likely provide more definitive future answers to the questions we still face in the interim.

Alcohol Drinking↗
PubMed1990

Assessing threats to the validity of experimental and observational designs.

Experimental designs, particularly the randomized trial, are viewed as the most scientifically rigorous methods by which knowledge is attained. Most clinical disciplines, however, use observational study designs more frequently than experimental designs. Nevertheless, the scientific rigor of experimental designs can be approximated by observational designs if common internal validity threats are recognized and addressed during the development of the research protocol. This paper presents a model of threats that can be applied to both types of designs to compare their scientific merits.

Case-Control Studies↗
PubMed1989

Baseline measurement of bone mass predicts fracture in white women.

STUDY OBJECTIVE: To determine if a single bone mass measurement of the radius is predictive of future fractures at any site. DESIGN: Observational study of a cohort of free-living subjects and a cohort of retirement-home residents with an average follow-up of 6.7 years and 5.5 years, respectively (range, 1 to 15 years for both cohorts). SETTING: General community and a retirement home. SUBJECTS: Volunteer sample of white women (386 free-living and 135 living in a retirement home) who were free of disease and were not receiving medication known to affect bone metabolism. In terms of physical condition subjects ranged from the totally independent to the wheelchair-bound. MEASUREMENTS AND MAIN RESULTS: A radial bone mass measurement was done at the initial visit. Subsequent non-spine fractures were reported by the subjects at follow-up visits, which were less than a year apart in most cases, and verified with medical records. Cox regression was used to model time to first fracture as a function of age and bone mass. These analyses showed that for every 0.1 g/cm decrement in bone mass, the relative risk of fracture was 2.2 (CI, 1.7 to 2.8) for the free-living and 1.5 (CI, 1.2 to 1.9) for the retirement-home residents. Baseline age did not predict the risk of fracture in either cohort, and controlling for baseline age did not reduce the relative-risk estimates of bone mass. Similar analyses also showed that bone mass was a statistically significant predictor for first hip fractures (n = 30) among the nursing-home residents (relative risk, 1.9; CI, 1.4 to 2.7) and first forearm fractures (n = 10) among the free living (relative risk, 3.6; CI, 1.9 to 6.8). For both cohorts, the 8-year probability of any nonspine fracture was about 80% for subjects with initial bone mass less than 0.6 g/cm and was less than 10% for subjects with initial bone mass greater than 0.8 g/cm. Similarly, those in the retirement home with bone mass below 0.6 g/cm had a 6-year probability of hip fracture of 43%, compared with a 17% risk for those with greater bone mass. CONCLUSION: A single bone mass measurement of the radius is predictive of future nonspine fractures at all sites, and at both the forearm and the hip. Baseline age was not a significant predictor of fracture within either cohort. Relative-risk estimates were not dissimilar across fracture sites.

Adult↗
PubMed1991

Probability of appendicitis before and after observation.

STUDY OBJECTIVE: To examine patients with abdominal pain for changes in probability of appendicitis during observation. STUDY DESIGN: Retrospective cohort study. SETTING: University-affiliated community hospital. METHODS: 252 patients with abdominal pain who were examined underwent short-term (10.4 hours) observation (95% confidence interval [CI], 8.7, 12.1) before the decision to operate during a one-year period. Alvarado's scoring system and a probability-of-diagnosis nomogram were used to assign scores and estimate probability of appendicitis. MEASUREMENTS AND RESULTS: In the study group, mean score of patients with appendicitis increased after observation from 6.8 (95% CI, 6.2, 7.4) to 7.8 (95% CI, 7.3, 8.3), corresponding to a change in probability of appendicitis from 50% to 65%. Mean score of patients without appendicitis decreased from 3.8 (95% CI, 3.5, 4.1) to 1.6 (95% CI, 1.58, 1.62), corresponding to a change in probability from 35% to 22%. The difference between mean scores for patients with and without appendicitis increased from 2.6 (95% CI, 2.0, 3.2) to 6.2 (95% CI, 6.15, 6.25) during observation. The study group initially had intermediate probability of appendicitis (score, 4.35; 95% CI, 4.04, 4.66) compared with high probability for patients who went directly to surgery after their initial evaluation (63 patients; score, 7.59; 95% CI, 7.05, 8.73) and low probability for patients with abdominal pain who were sent home after their initial evaluation without observation or surgery (2,097 patients; score, 1.87; 95% CI, 1.48, 2.26). CONCLUSION: In this group of patients with intermediate initial probability of appendicitis, observation improved the ability to distinguish patients with from those without appendicitis.

Abdominal Pain↗
PubMed1992

[Treatment of acid-related diseases of the gastrointestinal tract. Observations in patients receiving a single evening dose of 300 mg ranitidine].

UNLABELLED: Testing of the effectiveness and tolerability of ranitidine treatment in acid-related diseases of the gastrointestinal tract in non-selected outpatients. STUDY DESIGN: Observations made by 15,180 general practitioners and internists in the Länder of former West Germany in the period January 1989 to December 1990. PATIENTS: 23,783 patients with acid-related diseases of the gastrointestinal tract for which treatment with ranitidine is indicated (no further diagnostic or therapeutic requirement). TREATMENT: 300 mg ranitidine administered in the form of a single evening dose. RESULTS: A duodenal ulcer presented in 50.1%, a gastric ulcer in 26%, and reflux esophagitis in 29.6% of the patients; in 17.5% some other gastrointestinal disease (for the most part gastritis) was diagnosed. Six weeks of treatment was associated with a high rate of healing (more than 90%). The total incidence of side effects was a very low 0.77% (183 cases). These results confirm the effectiveness and good tolerability of ranitidine.

Adult↗
PubMed1990

Developing improved observational methods for evaluating therapeutic effectiveness.

Therapeutic efficacy is often studied with observational surveys of patients whose treatments were selected nonexperimentally. The results of these surveys are distrusted because of the fear that biased results occur in the absence of experimental principles, particularly randomization. The purpose of the current study was to develop and validate improved observational study designs by incorporating many of the design principles and patient assembly procedures of the randomized trial. The specific topic investigated was the prophylactic effectiveness of beta-blocker therapy after an acute myocardial infarction. To accomplish the research objective, three sets of data were compared. First, we developed a restricted cohort based on the eligibility criteria of the randomized clinical trial; second, we assembled an expanded cohort using the same design principles except for not restricting patient eligibility; and third, we used the data from the Beta Blocker Heart Attack Trial (BHAT), whose results served as the gold standard for comparison. In this research, the treatment difference in death rates for the restricted cohort and the BHAT trial was nearly identical. In contrast, the expanded cohort had a larger treatment difference than was observed in the BHAT trial. We also noted the important and largely neglected role that eligibility criteria may play in ensuring the validity of treatment comparisons and study outcomes. The new methodologic strategies we developed may improve the quality of observational studies and may be useful in assessing the efficacy of the many medical/surgical therapies that cannot be tested with randomized clinical trials.

Adrenergic beta-Antagonists↗
PubMed1991

Is neonatal inspired gas humidity accurately controlled by humidifier temperature?

OBJECTIVE: To investigate: a) the relationship between humidifier temperature and inspired gas humidity and b) the effect of insulating the inspiratory tube on "rainout" (condensate). DESIGN: Observational study. SETTING: Regional neonatal unit in a university hospital. PATIENTS: Forty-eight infants receiving assisted ventilation, of whom 31 infants were nursed in incubators and 17 under radiant heaters. MEASUREMENTS AND MAIN RESULTS: Despite always maintaining humidifier temperature greater than 34.7 degrees C, inspired gas humidity decreased below the American National Standards Institution minimum of 30 mg H2O/L on 35 of 479 occasions. At a humidifier temperature of 36 degrees C, inspired gas humidity varied between 17 and 43 mg H2O/L. In incubators set at a temperature of 34.1 +/- 1.3 (SD) degrees C, inspired gas humidity was linearly related to humidifier temperature, but with wide scatter (p less than .001, r2 = .28). In cooler incubators set at 32.9 +/- 1.8 degrees C, inspired gas humidity varied inversely with humidifier temperature. This variation was attributed to condensate due to inspired gas cooling within the incubator. Insulation of the inspiratory tubing reduced condensate by only 15%. CONCLUSIONS: Inspired gas humidity cannot be predicted reliably from humidifier temperature. Accurate control will require a new generation of humidifiers that measure inspired gas humidity.

Equipment Design↗
PubMedDate not supplied

Clinical predictors of treatment reduction in hypertensive patients.

OBJECTIVE: To demonstrate that some hypertensive patients under good blood pressure (BP) control can reduce medications, and to identify predictors of successful reduction. DESIGN: Observational study with 11-month follow-up. SETTING: Outpatient hypertension clinic at the Seattle Veterans Administration Hospital. PATIENTS: 59 males (51% of those eligible) with diastolic BP less than 95 mm Hg for greater than or equal to 6 months; 57 patients (97%) completed the study. INTERVENTION: Gradual reduction of medications unless diastolic BP rose above 95 mm Hg. MEASUREMENTS AND MAIN RESULTS: Intensity of treatment with BP medications was assessed using a scale of their comparative "vigors." 35 patients (59%) reduced medications successfully. By the end of the study, systolic BP had risen by 8.2 +/- 12.3 mm Hg (mean +/- SD) in successful patients, while diastolic BP did not change significantly. Two predictors of treatment reduction were statistically significant in both univariate and multivariate analyses: successful patients had been treated more intensively (2.7 +/- 1.7 vs. 1.3 +/- 0.5 "vigor units," p = 0.0001), and they had been enrolled in the clinic longer (5.5 +/- 3.0 vs. 3.1 +/- 2.3 years, p = 0.003). Lower systolic BP, higher urinary sodium excretion, lower compliance, and younger age were significant predictors of treatment reduction on univariate analysis only. Age less than or equal to 65 years had the highest sensitivity (86%) for treatment reduction, while treatment with two or more "vigor units" had the highest specificity (79%) and likelihood ratio (3.3). CONCLUSIONS: Treatment reduction is feasible in many well-controlled hypertensives, though systolic BP rises. Patients with high intensity and long duration of treatment are most likely to reduce medications successfully.

Antihypertensive Agents↗
PubMedDate not supplied

Evaluation of research studies. Part II: Observational studies.

Clinical practice is often based on the results of research. Critical evaluation of research studies is important if appropriate conclusions are to be drawn. In this series of columns, we review principles of research methodology and statistical analysis. Our intent is to assist certified nurse-midwives in understanding the relative merits of the research they read and use. This paper, the second of the series, will review issues pertinent to observational study design.

Humans↗
PubMed2026

Estradiol dynamics during superovulation are associated with oocyte quantity and maturation stage in cynomolgus macaques.

OBJECTIVE: To examine whether dynamic changes in circulating estradiol during ovarian stimulation are associated with the number and maturation status of oocytes recovered in cynomolgus macaques. DESIGN: Observational study based on retrospective analysis of ovarian stimulation cycles. SUBJECTS: Sixty-six ovarian stimulation cycles from adult female cynomolgus macaques (Macaca fascicularis) housed at the Primate Resources Center. EXPOSURE: Animals underwent a standardized gonadotropin-based ovarian stimulation protocol. Circulating estradiol concentrations were measured at multiple time points during the late follicular phase before oocyte recovery, and estradiol dynamics were defined as the difference between the maximum and minimum values observed across these measurements. MAIN OUTCOME MEASURES: Total number of oocytes recovered per stimulation cycle, number of mature oocytes at the metaphase two stage, and proportional distribution of oocyte maturation stages. RESULTS: Dynamic changes in estradiol concentrations were positively associated with the total number of oocytes recovered per cycle (correlation coefficient 0.45). A similar but weaker association was observed with the number of mature oocytes recovered (correlation coefficient 0.36). In contrast, estradiol dynamics were not associated with the proportional distribution of oocyte maturation stages. Donor age and body weight were not significantly associated with oocyte recovery outcomes. CONCLUSION: Dynamic changes in circulating estradiol during ovarian stimulation primarily reflect the quantitative dimension of ovarian response in cynomolgus macaques, with limited relevance for the maturation stage composition of recovered oocytes.

Animals↗
PubMed1991

Assessment of urinary symptoms in early pregnancy.

OBJECTIVES: To determine the correlation between lower urinary tract symptoms and urodynamic findings in early pregnancy. SETTING: The termination clinic and gynaecology ward at King's College Hospital. DESIGN: Observational study. SUBJECTS: 47 women before termination of pregnancy at between 6 and 15 weeks. INTERVENTIONS: Women filled in symptom questionnaires and then had urodynamic investigations, consisting of uroflowmetry and subtracted provoked cystometry. MAIN OUTCOME MEASURES: The occurrence of lower urinary tract symptoms and their association with urodynamic findings. RESULTS: Lower urinary tract symptoms were fairly common but there was poor correlation with the urodynamic findings. CONCLUSIONS: The findings suggest that lower urinary tract symptomatology alone is insufficient to study lower urinary tract dysfunction in pregnancy.

Adolescent↗
PubMed1992

Spontaneous fetal reduction in multiple gestations assessed by transvaginal ultrasound.

OBJECTIVE: To assess the occurrence of disappearance of one or more of the fetuses in pregnancies which start as multiple gestation. DESIGN: Observational study. SETTING: Infertility section, Rambam Hospital, Haifa. SUBJECTS: 88 women with multiple gestations, established after ovulation induction (54 twin, 26 triplet, five quadruplet, and three quintuplet) and diagnosed by transvaginal ultrasound at 5-6 weeks, in all of whom absorption of at least one gestation sac was detected at follow-up ultrasound scan. INTERVENTIONS: Follow-up by serial transvaginal and later abdominal ultrasound scan throughout pregnancy. RESULTS: Of the 54 twin gestations, 51 ended in the birth of a singleton and three in miscarriage. Of the 26 pregnancies starting as triplets, 12 ended in singleton births, 12 in twins and two miscarried. The five quadruplet gestations resulted in one singleton birth, one set of twins, two triplets, and one ended in late miscarriage. Of the three quintuplet pregnancies, two resulted in the birth of triplets, one of them after spontaneous, the other after iatrogenic fetal reduction. In the third quintuplet pregnancy, one fetus vanished spontaneously and another was subject to iatrogenic reduction, two fetuses survived and were liveborn. Of the 221 fetuses identified 107 (48%) vanished spontaneously. CONCLUSION: Iatrogenic fetal reduction should be delayed until 12 weeks gestation in quadruplet or higher multiple gestations, but is probably not indicated in twin and triplet gestations.

Adult↗
PubMed1992

A simplified method of laparoscopic presacral neurectomy for the treatment of central pelvic pain due to endometriosis.

OBJECTIVE: To describe optimal procedures and preliminary results for videolaparoscopic presacral neurectomy as part of the surgical treatment of endometriosis associated with intractable dysmenorrhoea. DESIGN: Observational study with follow up for at least one year. SETTING: Subspecialty practice: Endometriosis Clinic and Centre for Special Pelvic Surgery. SUBJECTS: Eighty five women (18-45 years) with endometriosis and intractable pain, referred because medical and surgical management had failed. Subjects without a central (midline) component to their discomfort were excluded. INTERVENTIONS: Excision and vaporization of endometriotic pathology was followed by presacral neurectomy. OUTCOME MEASURES: During surgery, severity of endometriosis was assessed using revised American Fertility Society scoring. Overall pelvic pain and dysmenorrhoea relief were determined by office visit, telephone interview and questionnaire at a minimum of one year postoperatively. RESULTS: There were no operative complications and all women left hospital within 24 h of surgery. Overall pain relief was reported by 49 (94%) of 52 patients followed. The other three subjects noted no pain abatement. Dysmenorrhoea was reduced in 48 (92%) whereas four (8%) women claimed no relief. CONCLUSIONS: Laparoscopic presacral neurectomy is an option for treating dysmenorrhoea and pelvic pain in selected women, but is indicated only if medical management has failed. Videolaparoscopic presacral neurectomy using the CO2 laser is safe in trained hands. Pain relief achieved is within the range reported for laparotomy.

Adolescent↗
PubMed1992

Laparoscopic treatment of infiltrative rectosigmoid colon and rectovaginal septum endometriosis by the technique of videolaparoscopy and the CO2 laser.

OBJECTIVE: To present the technique and results of videolaparoscopy and the CO2 laser as a treatment for deep, infiltrative endometriosis of the rectovaginal septum, uterosacral ligaments, pouch of Douglas and anterior wall of the rectosigmoid colon. DESIGN: Observational study with 1-5 year follow up. SETTING: Sub-specialty practice: Endometriosis clinic and centre for special pelvic surgery. SUBJECTS: 185 women, aged 25-41 years. All had pelvic endometriosis and were referred because of the failure of previous medical and/or surgical treatment. INTERVENTIONS: Vaporization and excision of endometriotic implants and nodules, ureterolysis, ureteric stents, laparoscopic anterior rectal wall resection and reanastomosis, presacral neurectomy, laparoscopic hysterectomy, salpingo-oophorectomy and appendicectomy using the CO2 laser. MAIN OUTCOME MEASURES: 174 patients were followed for 1-5 years after surgery by office visit questionnaire or telephone interview. Eleven were lost to follow-up. RESULTS: 175 patients were discharged within 24 h. Nine with bowel perforations and one with a partial bowel resection were discharged 2-4 days postoperatively. Two patients required ureteric stents, which were removed 6 weeks postoperatively without sequelae. 162 women reported moderate to complete pain relief (145 after one procedure, 13 after two and four after three). 12 reported persistent or worse pain following the surgery. Seven eventually underwent total hysterectomy, four had bowel resections and one had a salpingo-oophorectomy. Of 61 with infertility, 25 achieved pregnancy. Postoperative complications included shoulder pain, anterior abdominal wall ecchymosis, urine retention and dyschezia for one to two weeks. CONCLUSIONS: Our experience suggests that rectosigmoid colon and infiltrative rectovaginal septum endometriosis can be effectively treated via videolaparoscopy in the hands of experienced endoscopic gynaecologists.

Adult↗
PubMed1992

Normal amniotic pressure throughout gestation.

OBJECTIVE: To characterize amniotic pressure (AP) in pregnancies with normal amniotic fluid volume. DESIGN: Observational study, mainly cross-sectional. SETTING: Fetal medicine unit within a tertiary referral hospital. SUBJECTS: Patients undergoing transamniotic invasive procedures in whom amniotic fluid volume was subjectively assessed as normal on ultrasound. Those beyond 16 weeks with a deepest vertical pool on ultrasound less than 3.0 or greater than 8.0 cm were excluded. Overall 194 pregnancies were studied on 232 occasions between 7 and 38 weeks gestation. INTERVENTIONS: Manometry readings referenced to the top of the maternal abdomen were obtained via a fluid-filled line from the needle hub and either connected to a pressure transducer (n = 190) or held vertically against a ruler (n = 42). MAIN OUTCOME MEASURES: AP in mm Hg, AP corrected for gestational age (z scores), semi-quantitative ultrasonic indices of amniotic fluid volume, clinical variables. RESULTS: AP in singleton pregnancies increased with advancing gestation (P less than 0.001), and the sigmoid-shaped regression curve plateaued in the mid-trimester. AP z scores were not influenced by volume-related phenomena such as twin gestation, the deepest vertical pool, or amniotic fluid index, nor by maternal age, parity, gravidity, fetal sex, or subsequent spontaneous preterm delivery. CONCLUSIONS: These findings suggest that AP is not principally determined by intrauterine volume. We speculate that AP, which reflects change in uterine tension as a function of radius, may instead be determined by gestation-specific anatomical and hormonal influences on gravid uterine musculature. A reference range for AP has been constructed for use in amnioinfusion and amnioreduction procedures.

Amniotic Fluid↗
PubMed1992

The treatment of intrahepatic cholestasis of pregnancy by dexamethasone.

OBJECTIVE: To investigate whether dexamethasone suppression of fetoplacental oestrogen production can reduce obstetric cholestasis. DESIGN: Observational study. SETTING: Department of Obstetrics and Gynaecology, University of Tampere, Finland. SUBJECTS: 10 women, at between 28 and 37 weeks gestation, with intrahepatic cholestasis of pregnancy. INTERVENTIONS: Treatment with 12 mg oral dexamethasone daily for 7 days, after which the therapy was gradually discontinued over 3 days. MAIN OUTCOME MEASURES: Serum oestriol, oestradiol, total bile acids and ALAT were measured before and during therapy and on days 4 and 7 and ALAT also on day 12. Differences were tested by paired t test. RESULTS: Itching disappeared or was relieved in all patients. Serum oestriol level fell significantly by day 1 of treatment, serum oestradiol and total bile acid levels by day 4 and ALAT by day 12 from the beginning of the therapy. CONCLUSION: Dexamethasone is a drug of choice in the treatment of intrahepatic cholestasis of pregnancy.

Cholestasis, Intrahepatic↗